Delivery systems which act as a vehicle to deliver an active agent in vivo are known and are designed primarily to a specific biomedical application. Some systems not only merely act by just carrying the active agent but are specifically designed to deliver the active in a more efficient manner. For instance, when such systems are designed there is particular emphasis on parameters such as mode of delivery (e.g., oral, topical, transmucosal, etc.), drug release profile, as well as ADME properties (Adsorption, Distribution, Metabolism and Excretion) of the drug in vivo.
Many biological active agents such as peptide/proteins, antibodies, vaccines and gene based therapeutics may not be effectively delivered using, for instance, the oral and transmucosal routes. Such therapeutics are often quite susceptible to enzymatic degradation or are insufficiently absorbed into the systemic circulation due to molecular size and/or charge. As such, many of these therapeutics are delivered by injection. For instance, many vaccines are based on the delivery of protein based drugs intravenously.
Also, typically, the administration of a biological active agent to a subject requires repeated administration of the active over a period of time in order for the active to provide the required effect. For example, immunization through the short term vaccination process has logistical and commercial disadvantages because it requires multiple vaccinations, boosters and high doses of vaccine generally, which result in increased cost to both industry and the end-users.
To date, vaccines are often delivered to a subject in the form of a dispersion (which can be solid or emulsion or liquid/liquid dispersions) or in particulate form, including microparticles, emulsions, immune stimulating complexes, liposomes, virosomes and virus-like particles.
However, despite the success of methods of initiating an immune response to an antigen they still require the antigen to be administered repeatedly to a subject. A similar problem occurs in the administration of numerous other drugs to subjects.
Accordingly, a need has evolved to develop drug-delivery systems for prolonged and better control in drug administration. The present invention seeks to address at least some of the shortcomings of the known delivery systems.